Plantar aponeurosis

What is the structure of the plantar aponeurosis?

The plantar fascia is significantly thicker than the dorsal fascia of the foot. Extending onto the sole, it forms a robust plantar aponeurosis. Like other aponeuroses in the body, it is a broad plate that ensures the correct orientation of the muscle pull vector.

Structurally, the aponeurosis consists of two types of fibers:

• Longitudinal bundles — extend from the calcaneal tuberosity to the bases of the proximal phalanges of digits II–V. These bundles are most prominent in the central part of the sole.
• Transverse bundles — participate in the formation of the superficial and deep transverse metatarsal ligaments (ligg. metatarsalia transversa superficialia et profunda).

Topography and formation of fascial compartments

The plantar aponeurosis forms the inferior wall of the plantar fascial space (the superior wall is formed by the deep fascia in the metatarsal region, and by the long plantar ligament and tarsal bones in the tarsal region).

The medial and lateral intermuscular septa (septa intermuscularia plantae mediale et laterale) serve as the lateral walls, dividing the sole into three fascial compartments:

• Medial compartment — bounded laterally by the medial septum. It contains the abductor hallucis muscle (m. abductor hallucis) and the tendon of the flexor hallucis longus.
• Central compartment — bounded deeply by the plantar interosseous fascia. It contains the flexor digitorum brevis (m. flexor digitorum brevis), the tendons of the flexor digitorum longus and brevis, the lumbrical muscles, and the adductor hallucis.
• Lateral compartment — bounded medially by the lateral septum. Includes the abductor digiti minimi and flexor digiti minimi brevis muscles.

Additionally, the aponeurosis is closely connected with the fat pads of the sole and the tendon sheaths, forming fibrous tunnels for the common flexor tendons.

Relationship with muscles and ligaments

The plantar aponeurosis is an essential part of the musculo-ligamentous apparatus of the foot:

• It is part of the ligamentous complex of the foot alongside the long plantar, calcaneocuboid, calcaneonavicular, and plantar cuneonavicular ligaments.
• It serves as one of the origin points for the flexor digitorum brevis (m. flexor digitorum brevis). This muscle originates from the medial process of the calcaneal tuberosity and directly from the plantar aponeurosis itself, then extends toward the middle phalanges of digits II–V.

Clinical significance

A number of pathological conditions are associated with the plantar aponeurosis:

• Plantar fasciitis — a clinical syndrome associated with damage to this structure.
• Enthesopathies — pathology of the sites of attachment (enthesis) of tendons, ligaments, or joint capsules to bone. The plantar fascia is a typical localization for enthesopathies. It manifests as spontaneous pain or tenderness upon palpation. This condition is of major diagnostic significance as it is a characteristic sign of seronegative spondyloarthropathies — a group of genetically predisposed inflammatory diseases affecting the spine and peripheral joints.

Class and exam questions

What else to study on this topic

• Fascial compartments of the foot and intermuscular septa
• Flexor digitorum brevis (m. flexor digitorum brevis)
• Ligamentous apparatus of the foot
• Enthesopathies and spondyloarthropathies

Other topics in the "Anatomical Structures" section

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